Insulation systems for Nb3Sn accelerator magnet coils manufactured by the Wind & React technique

Superconducting dipole and quadrupole magnets for particle accelerators and storage rings usually rely on saddle-shaped coils wound from Rutherford-type cables. When using Nb3Sn, the small radii of curvature of coil ends impose that the winding be performed with un-reacted conductors and that the heat treatment needed for Nb3Sn compound formation be applied on the whole coil upon winding completion. This results in very stringent requirements on the cable insulation system, which must be able to sustain the high-temperature cycle while retaining its mechanical strength and avoiding the formation of deleterious carbon compounds. Furthermore, it is also desirable to integrate the insulation system as a means of conferring a rigid shape to the manufactured coils, in order to ease subsequent handling and assembly and to protect the brittle material. We review here how various accelerator magnet R&D programs around the world are presently dealing with these issues.